1. Field of the Invention
This invention relates to a foundry sand blowing apparatus for blowing foundry sand into a mold in forming a die such as a core for use in shell mold process or the like.
2. Description of the Prior Art
Generally a die such as a core is formed by blowing, under air pressure, foundry sand coated with foundry resin into a cavity of a split mold through a sand blowing port formed in a part of the mold, and heating the mold to melt the foundry resin to bind and set the foundry sand in a shape conforming to the shape of the cavity. In this method, the set product is removed from the mold by means of an eject pin. That is, since the product produced by such a method is held on the part of the mold in which the blowing port is formed when the mold is opened, the eject pin is inserted into the blowing port from outside the mold after the mold is opened to force out the product from the mold.
Conventionally, an apparatus for forming a core or the like in accordance with this method is provided, as disclosed in Japanese Unexamined Utility Model Publication No. 58(1983)-43848, with a blow station at which foundry sand stored in a foundry sand storage tank is blown into a mold (blowing step), and an ejection station at which a product is removed from the mold by operation of an eject pin (ejecting step).
However, the conventional apparatus is disadvantageous in that the mold must be reciprocated between the blow station and the eject station each time a product is formed, thereby increasing the cycle time by the time required for the reciprocation of the mold, and that the apparatus becomes cumbersome since both a blow station and an eject station must be provided.
Further, there has been known a sand blowing apparatus in which the foundry sand blown into the cavity of the mold is cured by curing catalyst gas introduced into the cavity as disclosed in Japanese Patent Publication No. 48(1973)-9246. (This method is generally referred to as the "cold-box method".) Also, in this apparatus, the mold must be reciprocated between the blow station and the eject station each time a product is formed. Further, in the cold-box type apparatus, there has been a problem that the curing catalyst gas cannot be permitted to leak outside since it is toxic and that if the curing catalyst gas is brought into contact with virgin sand in the sand storage tank, the sand is cured.